Scanning probe microscopy (SPM) is a technique for measuring in nanoscale the surface profile of a sample or a variety of physical properties and functions of the sample surface by scanning the sample surface with a sharp-pointed probe. In recent years, scanning probe microscopes having a plurality of probes have been developed with the aim of more accurately measuring the surface profile and a variety of physical properties and functions of a sample.
In such a scanning probe microscope having a plurality of probes, an optical microscope or an electron microscope is conventionally used to move the plurality of probes to the measurement position on the sample surface (refer to Patent Document 1).
In a scanning near-field optical microscope (SNOM), which is a kind of scanning probe microscope, a near-field light is generated around a probe positioned near a sample, and the light intensity or the optical characteristics of the scattered light generated by the interaction between the probe and the sample surface is measured to detect the surface condition of the sample. It is very important to accurately detect the distance between the sample surface and the probe tip and precisely control the position of the probe tip in order to realize a resolution beyond the diffraction limit of light.